>What, there are different pictures? How come none of the books
>and articles I've seen show a second picture?
The Men in Black have been at your house, ripping out the other picture.
The two `classic' frames are Viking 35A72 and 70A13.
According to a dismally stupid book called THE FACE ON MARS: THE EVIDENCE
OF A LOST MARTIAN CIVILIZATION (Brian Crowley and James J Hurtak, 1986):
`Then there are four additional very high altitude shots which, if blown up
to their limits, produce a resolution of the face about the size of a small
pea. The lighting from all four, however, is from the east and, through
enhancement techniques, it can be confirmed that a basic overall symmetry
is preserved [...]' No frame numbers are given in the text. They're bound
to be on the net somewhere.
The best explanation for this phenomenon is provided in my young adults' sf
novel THE SEA'S FURTHEST END (Adelaide, Australia: Aphelion, 1993), but
it's not available in the US or UK. Bad luck. :)